How To: USB hookup for computer while having ethernet hookup to Xbox 360.

Hi. Im trying to use the Westell modem for my Centurytel hookup for the internet. We've been using the ethernet cord and its been working fine. Now I have an Xbox 360 and I'm trying to get the modem to give internet connection to both my computer and my Xbox 360 at the same time. I would be using the USB cord for my computer, and a 25 foot ethernet cord for my Xbox 360. Can this work? How? Thanks